The present invention relates to a transfer belt unit which is mounted on a full color copying machine, a color printer and the like.
An image forming apparatus such as a full color copying machine, a color printer or the like has a process unit provided with four image forming portions (yellow, magenta, cyan and black) for forming the respective color images in parallel, and a transfer belt for conveying a paper through these four image forming portions. The transfer belt is tensioned around a pair of rollers which are arranged apart from each other, arranged below the process unit and rolls in contact with a photosensitive drum in each of the image forming portions.
Further, four transfer rollers are arranged in an inner side of the transfer belt in a positional relationship opposing to each of the photosensitive drum. Each of the transfer rollers functions so as to apply a high bias voltage from the inner side of the transfer belt, supply a high voltage to a paper adhered and held on the transfer belt in an electrostatic manner and conveyed, and transfer a toner image with each of the colors formed on a surface of the photosensitive drum on the paper in an overlapping manner.
In general, a drive roller and a driven roller around which the transfer belt is wound are rotatably mounted to a frame of the image forming apparatus. That is, the transfer belt is assembled in the image forming apparatus in a fixed manner. Further, a power supply portion for supplying a high voltage from a side of an apparatus main body is connected to each of the transfer rollers.
Accordingly, at a time of replacing the transfer belt or the transfer roller due to a service life, at first the process unit including four image forming portions is taken out from the image forming apparatus by a service operator. Thereafter, the transfer belt is taken out from the apparatus, a connection between the transfer roller and the power supply portion is cancelled so as to take out the transfer roller from the apparatus, and a new transfer belt and a new transfer roller are mounted to the apparatus.
Further, in this kind of image forming apparatus, in the case that a jamming of the paper is generated between the process unit and the transfer belt, the process unit is taken out from the apparatus or the process unit is slightly tilted and moved apart from the transfer belt so as to form a slight space between the transfer belt and the process unit, thereby removing the paper.
However, in the conventional image forming apparatus mentioned above, in the case of replacing the transfer belt and the transfer roller by the new ones, it is necessary to take out the transfer belt from the apparatus and take out the connection between each of the power supply portions of the transfer rollers so as to take out the transfer rollers from the apparatus after temporarily taking out the process unit from the apparatus, so that there is a problem that it is troublesome to replace the transfer belt and the transfer rollers. Accordingly, the user can not replace the transfer belt and the transfer rollers and the replacing operation requires much load for the service operator. Further, as mentioned above, since much time is required for replacing the transfer belt and the transfer rollers, there is a problem that a time for which the apparatus is stopped for the replacing operation is increased, so that the rate of operation of the apparatus is reduced.
Further, in the conventional image forming apparatus mentioned above, in the case of treating the jamming of the paper clogged between the process unit and the transfer belt, in the apparatus of a type which is rotated upward around one end of the process unit so as to be tilted, it is impossible to sufficiently secure a treating space in the upstream side or the downstream side of the transfer belt, so that it is troublesome to remove the paper.